Method of and apparatus for controlling weft carriers in travelling-shed weaving machines

ABSTRACT

Method of and apparatus for controlling weft carriers in travelling-shed weaving machines. Resistance to the travel of the carriers during their movement as by an incompletely open shed is monitored by a scanning bar; the scanning bar is connected to a transducer which transmits a signal to a controller for the machine drive to stop the machine.

United States Patent [1 1 V- Bucll et al.

[ METHOD OF AND APPARATUS FOR CONTROLLING WEFT CARRIERS IN TRAVELLING-SHED WEAVING MACHINES [75] Inventors: Frantisiek Bucil; Vitzslav vasekg Karel Spatenka, all of Usti nad Orlici. Czechoslovakia [73] Assignee: Vyzkumny ustav bavlnarsky, Usti nad Orlici, Czechoslovakia [22] Filed: June 11, I973 [21] Appl. No.: 368,603

[30] Foreign Application Priority Data June 12. 1972 Czechoslovakia 4065-72 June I2, 1972 Czechoslovakia 4066-72 [52] U.S. Cl. 139/12 [51] Int. Cl D03d 47/26 Apr. 29, 1975 [58] Field of Search 139/l2, I3, 336, 340. 344

[ 56] References Cited UNITED STATES PATENTS 3.683.969 8/1972 Strauss v. 139/[2 3.729.029 4/l973 Zabrodsky et a] 139/12 Primary Exuminer-Henry S. .laudon [57] ABSTRACT Method of and apparatus for controlling weft carriers in travelling-shed weaving machines. Resistance to the travel of the carriers during their movement as by an incompletely open shed is monitored by a scanning bar; the scanning bar is connected to a transducer which transmits a signal to a controller for the machine drive to stop the machine,

21 Claims, 12 Drawing Figures PLIENYH APR 2 9 i975 SHEET 10F 6 PJ'JENTEE AFB 2 91975 SHEET l 0F 6 PLTENTEE APP. 2 9 i975 SNEET 5 OF 6 PATENTEU APR 29 i975 SHEEI 5 OF 6 METHOD OF AND APPARATUS FOR CONTROLLING WEFT CARRIERS IN TRAVELLING-SHED WEAVING MACHINES The invention has among its objects the provision of a method of controlling weft carriers in travelling-shed weaving machines and an apparatus for carrying out the said method.

When weaving on travelling-shed weaving machines undesirable adhesion of the warp threads. caused by impurities, may occur. Because of this an incompletely open shed is formed. This results in an increased resistance to travel of the carrier. and can cause serious difticulties with the apparatus.

The invention has among its objects the elimination of the said defect and the provision of a reliable method of controlling the carriers as well as the provision of an apparatus to carry out the said control in order to stop the weaving machine immediately in case of increased resistance to travel of the carrier induced by whatever trouble. i.e.. by irregularity of the carrier operation. in order to remedy the failure.

The method according to the invention comprises detecting an increased resistance to the carrier during the travel of the same induced by a deviation from normal operation. the scanning being carried out by means of a scanning bar controlling a transducer which signals the machine drive controller to stop the said machine.

Another feature of the invention is the monitoring of j the carrier separately in the entry end zone. in the entry transferring zone. in the shed zone. in the exit transferring zone. and in the exit end zone. the increased force component directed against the scanning bar. induced by the increased resistance to the carrier against the movement of the same. being detected by the scanning bar.

In the apparatus of the invention the scanning bar is preferably a part of the top guide for the carriers. and is engaged with the controller converter for stopping the machine.

A further feature ofthe apparatus is that the scanning bar is divided into parts including an entry end scanning bar. an entry transferring bar. and an exit end scanning bar. each ofsuch scanning bar parts being engaged with at least one converter or transducer of the controller for stopping the machine.

The adjacent scanning bar ends can be cut askew in order to prevent the warp threads from penetrating into the interstice between them.

Another feature is that the scanning bars are displaceable from an operating position to a nonoperating position and vice versa.

Further it is advantageous. when the entry end scanning bar. the entry transferring bar. the shed scanning bar. the exit transferring bar and the exit end scanning bar are displaceable from their operating position to their non-operating position and vice versa, that the shed scanning bar be divided into independent scanning sections displaceable into a non-operating position.

A further feature is that the scanning bar may be swingably mounted on an arm in the range of the stops. the scanning bar being pressed by a spring into its basic position, and the same when in scanning position being in contact with the transducer fixed on the said arm. It is then advantageous. when the stops are settable that the said arm be anchored on the shaft for deflecting the scanning bar into non-operating position.

Another feature is the provision of electrically nonconductive elastic bar members aligned between the scanning bar and a rigid cross-beam and a ribbon-like contact electrode placed against the scanning bar at a distance. such spacing being eliminated by the force which arises when trouble occurs. thereby establishing an electric conductive connection.

Another feature is the provision of a rigid beam anchored on a lift rod. the scanning bar consisting a part of such beam. and being mounted in an electrically insulated manner. and contact points mounted on the beam and directed toward the scanning bar.

According to another feature a condenser is arranged between the scanning bar and adjustable holders. the condenser changing its capacity when deflection of the scanning bar takes place.

Another advantageous feature is the provision of bellows of variable volume connected to a contact manostat arranged between the scanning bar and springloaded against the rigid cross-beam. and elastic members aligned between the scanning bar and the rigid beam. the rigid beam having stops. the rigid beam car rying the scanning bar being anchored on the draw rod of the lifting mechanism.

Non-limiting illustrative embodiments of the device according to the invention are diagrammatically illustrated in the enclosed drawings. wherein is FIG. 1 is a view of the weaving machine part with the top guide of the carriers;

FIG. 2 illustrates the track of the carriers;

FIG. 3 illustrates force relations with the carrier;

FIG. 4 shows the top guide of the carriers with the scanning bar;

FIG. 5 illustrates the top guide ofthe carriers with the scanning bar divided into several sections:

FIG. 6 shows the embodiment of the top guide section adapted for manual operation.

FIG. 7 shows one embodiment of a composite scanning bar adjacent the ends of the section thereof:

FIG. 8 shows one section of one embodiment electromechanical contact transducer.

FIG. 9 illustrates an embodiment ofa transducer with continuous scanning;

FIG. 10 illustrates an embodiment of a mechanical contact transducer with multipoint scanning:

FIG. 11 illustrates an embodiment of a contactless capacity transudcer: and

FIG. 12 illustrates an embodiment of the mechanicalpneumatic transducer.

Turning now to FIGS. 1-4 inclusive. on a cross-beam l of the weaving machine there is the top guide 2 of the weft carriers 3. the lower part of the guide 2 also forming the shed scanning bar 20. In FIG. 1 underneath the top guide 2 there is shown a carrier 3 as well as a chain 3] which drives the carriers 3. In front of the shed scanning bar 20 (FIG. 2) there are. reading from right to left. an entry end scanning bar 2] and an entry transferring scanning bar 22; beyond (to the left of) the shed scanning bar 20 there follow an exit transferring scanning bar 23. and an exit end scanning bar 24.

The entry end scanning bar 21 is in the area of the entry end zone A of the carriers; the entry transferring scanning bar 22 is in the area of the entry transferring zone B; the shed scanning bar 20 is in the area of the shed zone C; the exit transferring scanning bar 23 is in the area of the exit transferring zone D. and the exit end scanning bar 24 is in the area of the exit end -zone E of the carriers 3.

Each of the scanning bars 20 to 24 is connected to a switch element 40, 41, 42. 43, 44. each switch element 40. 41, 42, 43. 44 is also connected to the controller 45 of the machine drive P (FIG. 3).

FIG. 3 shows in simplified form the force relations of the weft carrier 3 in motion with respect to its environment. The driving member of the carrier 3 is the link 310 of the chain 31. acting by means of the pulley 311 (FIG. 2) on the pulley 312 mounted pivotally in the body of the carrier 3 during the partial vertical alighment of the pulleys 311. 312 in the direction H of movement of the carriers. The thus arranged geometry of the driving pulley 311 and the driven pulley 312 requires support; this is supplied by the shed scanning bar 20 of the top guide 2. In the illustrated resolution of forces which occur with the driving of the carrier 3. the most important is the vertical component of the force Fy. The force Fy is affected on one hand by the angle alpha and on the other hand by the resistance S. The resistance S is variable from the practical viewpoint during the machine run. especially when an incompletely open shed 410 occurs by reason of adhesion of two adjacent warp threads.

The described case of the increased resistance 5" against the carrier 3 causes the increase of the vertical force component F as well against which the reactive force R arises and force balance failure in the mecha nism ofthe shed scanning bar ofthe top guide of the carrier 3 occurs. This action is advantageously employed in such a way as to scan by suitable means the force extremes of the vertical force component F v and use the same for stopping the machine in case of the fabric quality reduction or the endangering of the machine mechanism. That means that increased resistance 5 to the carriers 3 developed against the movement of the same. especially in the shed. induced by the deviation from the normal operation, is scanned by the scanning bar 20 or by other above-described scanning bars. controlling the respective transducer whose signal is forwarded to the controller 45 for stopping the machine drive. The scanning bars 20 and 24 are anchored in such a way as to form a fixed top guide for the same during the normal motion of the carriers 3, whilst in case of increased resistance to movements of the carrier. moving in such manner as to make each of the converters 40 to 44 react reliably.

A switch element 401 is coupled with the scanning bar 20. The switch element is connected to the positive pole. designated by of a current source and via the relay as a controller 45 to the negative pole. designated by of the current source. The machine drive P is connected via contacts 451:. controlled by the controller 45 to the network voltage.

The shed scanning bar 20 is carried by arms 25 anchored on a shaft 26. In order to put the shed scanning bar 20 into non-operating position. the shaft 26 is driven by means of an electric motor 28 through a worm and wheel 27. Manual drive of the shaft 26 by means of a crank 280 is possible with the embodiment of FIG. I. The entry end and exit end scanning bars 22 and 23 are connected with the shaft 26 by a rock 29 which meshes with a pinion 290. The shaft 26 is journalled in brackets 260 anchored on the cross-beam 1.

By rotating the shaft 26. the shed scanning bar 20 is released from the operating position to the nonoperating position. e.g. in order to remedy failures. the entry transferring scanning bar 22 and the exit transferring scanning bar 23 also rising with scanning bar 20. The entry end scanning bar 21 and the exit end scanning bar 24 are lifted manually as by a lever 210. Means mounting the scanning bars 21, 22, 23 and 24 are not illustrated in detail. These bars can be mounted for ex ample by means illustrated in FIGS. 8. 9, 10, 11 and 12.

In the embodiment according to FIG. 4, one single shed scanning bar 2000 is used, the same being fixed on the arms 25. Arms 25 are engaged with the shaft 2600 driven by a hand crank 2801.

In the embodiment of FIG. 5, there are employed a plurality of shed scanning bars 201, 202, 203 rather than a single shed scanning bar. Each of bars 201, 202 and 203 form an independent scanning section and are connected to an independent sensor 4010. 4020. 4030.

The arms 2501 are fixedly attached to the shaft 261. The individual scanning sections are arranged in such a manner as to be partially swingable with the arms 25 by means of transverse arms 250. 251 equipped with hinges 252 and pins 25. each bar section is adjusted into operating position by a pressure spring 254 and stops 255.

FIG. 6 illustrates an embodiment of a scanning bar adapted for manual operation. A shed scanning bar 2021 with a build-in transducer 402] is suspended on an arm 2502 swingable round the pins 2610 of the brackets 2602 and is equipped with a holder 256. On one of the brackets 2602 (the left hand one). there is affixed an induction sensor 263. The right hand bracket 2602 is equipped with an electromagnetic lock 262 which secures the arm 2502 in its operating position long as the machine is in operation. whereas an induction sensor 263 prevents the machine from starting as long as the arm 2502 is in non-operating position. The catch of the electromagnetic lock 262. also selectively holds the arm 2502 in raised. deflected position. The height of the shed scanning bar 2021 may be adjusted by the clamping collar 264 which is with a nut 265.

In FIG. 7 the adjacent ends of the scanning bars. in the given case the shed scanning bars 202 and 203. are cut askew in order to prevent the warp threads 411 from penetrating into the gap between the two bars.

FIG. 8 shows in detail an embodiment of the electro magnetic contact transducer of the increased force from the non'illustrated carrier, transfered by a shed scanning bar 2001 on a bottom lateral arm 96 mounted swingably by means of the pin 97 and the hinge 98 on a top lateral arm 99 forming a lever system. There is a pressure spring mounted between both lateral arms 96. 99 as a reactive nominal force acting against the force from the carrier. The mutual permitted deflection around pin 97 of the lateral arms 96, 99 is adjusted by a screw 91 in a nut 92 secured to arm 96 and a screw 91 in the upstanding mechanical stop 93 on arm 96.

The bottom lateral arm 96 is equipped with a rod 990 transferring the upward deflection of the scanning bar 2001 shown by the arrow 95 by means of the bottom lateral arm 96 into a switch or transducer 400. The switch 40 is interposed in an electrical circuit leading to a non-illustrated electic control unit for the machine. The described assembly of FIG. 8 is mounted on a vertical arm 2503 fixedly connected with the shaft 261 I in order to move the scanning bars 200] from an operating to an auxiliary non-operating bar. FIG. 9 shows a transducer comprising a rigid cross-beam 440. which is arranged on the stirrup of rod 4001. A pin 450 is used to connect the rigid cross-beam 440 with the stirrup of rod 4001.

To the bottom areas 460 of the rigid cross-beam 440 there are fixed endways two bars 4701. 4702 of elastic and electrically non-conductive material such as rubher. the scanning bar 2002 being affixed to bars 4701. 4702 in such manner as to produce an assembly of parts which is closed in cross-section. the rigid crossbeam 440 and the scanning bar 2002 are electrically insulated from each other by the members 4701. 4702.

A cavity 490 is formed between the rigid cross-beam 440 and the scanning bar 2002; into such cavity there is built-in a ribbon-like contact electrode 50; the lower edge of the electrode 50 having endways arranged blade 51 or sawtooth teeth 52 or both. The space 53 between the scanning bar 2002 and the blade 51, on the one hand. and the teeth 52 and bar 2002. on the other. is selected by advancing the holder 54 in an insulating guide sleeve 55 which is firmly coupled with the rigid cross-beam 440 and is secured by a screw 56. The adjustment of the space 53 is dependent on the compressibility of the members 4701. 4702. the longitudinal elasticity and the required sensitivity of the scanning bar 2002. Two conductors 57. one of which is electrically connected with the scanning bar 2002 and the second of which is connected with the ribbon-like contact electrode 50 by means of the holder 54 are designed to transfer electric signals.

The embodiment of the sensor shown in FIG. 9 cmploys the longitudinal elasticity of the scanning bar 2002 whilst in crosswise direction the scanning bar is virtually a rigid element. The rigid cross-beam 440 incorporates mechanical stops 58. The distance between the stops 58 and scanning bar 2002 is slightly greater than the space 53 between the scanning bar 2002 and the blade 51. Such stops protecting the built-in contact elements from damage in extraordinary cases when the pressure from the carriers upon the scanning bar 2002 is substantially exceeded.

P10. shows another embodiment of the transducer with multi-point scanning. Such embodiment incorporates a rigid beam 59 and a reinforced beam 60. the two beams being electrically insulated from one another by an electrically insulating insert 6] of ribbon-like shape. such parts forming a common rigid entity.

The scanning bar 2003 and an auxiliary angular piece 63 are further connected electrically. conductively to the beam 59. the resulting scanning bar considered in cross-section being a unilaterally fixed beam.

The free end of the scanning bar 2003 is equipped on its lower surface with a reinforced pad 64 of ribbon-like shape to the bottom surface of which the force from a non-illustrated carrier is transferred.

The top surface of the scanning bar 2003 is accessible to contact with electrical contact points 65 which are spaced at predetermined distances over the entire functional length ofthe reinforced beam 60. The space 531 between the contact point 65 and the scanning bar 2003 is adjustable by turning the screw 67. the screw being secured in adjusted position by the lock nut 68.

The rigid beam 59 and the beam 60 are electrically connected with conductors 57 for electric signal transfer. The hitherto describcd assembly of parts form a compact entity which is suspended in the stirrup by a pivot pin 450 and two spacer washers 69'. the pin 450 as well as the washers 69 being made of electrically non-conductive material. The stirrup is fixedly connected with the toothed rod 29 of the lifting mechanism and the shaft 2612. respectively. The reinforced beam 60 incorporates mechanical stops 58. The distance between the stops 581 and scanning bar 2003 is slightly greater than the space 531 between the contact point and the scanning bar 2003. stops protecting the contact points 65 from damage in cases which have already been described.

FIG. 11 shows the embodiment of the apparatus employing a capacitive transducer. The rigid cross-beam 4401 together with two bars 4703. 4702 of eleastic material and the scanning bar 2004 form a closed cavity 4901 in the cross-section. On the inner side of the scanning bar 2004 there is a tape foil developed in strip shape along the length of the same. the foil forming the bottom electrode 70 of a condenser. Above the tape foil there are surface foil systems arranged in selected spacings on holders 71 and forming the top electrode 72 of the said condenser; there is a space 532 between such two electrodes corresponding with the required function and sensitivity of the thus formed variable condenser functioning as a sensor.

The surfaces of both electrodes 70. 72 are equipped with an electrically insulating protecting layer 74 preventing an eventual failure of the capacity electric circuit. The said holders 71 are seated in insulating conductive sleeves 551 and after the adjustment in height of the same. they are secured by a screw 56!.

The conductor 76 of each individual top electrode 72 is led through the cavity of the holder 71. while the bottom tape electrode 70 has a common conductor 77.

The rigid beam 4401 has mechanical stops 582. The distance between the stops 582 and scanning bar 2004 is slightly greater than the space 532 between two electrodes 70. 72 of said condensor. Such stops protect the built-in condenser elements from damage in extraordinary cases when the pressure from the carriers is substantially exceeded.

The beam 440] is suspended by means of the toothed rod 292 of the lifting mechanism. The rod has a stirrup on its lower end. the beam 4401 being pivotally connected to the stirrup by a pivot pin 4502.

FIG. 12 shows an embodiment of the apparatus employing a pneumatic sensor. The rigid beam 4402 together with the bars 4705, 4706 and the scanning bar 2005 form a closed cavity 4902 in the cross-section of which bellows 80 are built-in. On the face side. the bellows 80 are attached to pipe 81 whilst the other face wall of the bellows is equipped with an adapter 84 touching the scanning bar 2005. The pipe 81 is equipped with an external thread 85 and. by the rotation of the same in a nut 86 which is coupled firmly with the beam 4402. the bellows 80 can be adjusted to a basic position and secured in such position by a lock nut 87.

The deformation of the scanning bar 2005 is transferred by the adapter 84 on the bellows 80. the same being compressed and thereby inducing a change of the inner volume of the bellows and simultaneously changing the pressure of the gaseous medium in the bellows. The described pressure changes are evaluated by a non-illustrated contact manostat interconnected with the tubes 88. In the case of increased pressure of the carrier. the said manostat transmits an electric impulse into the central machine controller thereby to induce the interruption ofthe weaving process. The bellows 80 is protected against damage by means of mechanical stops 583. Between the stops 583 and scanning bar 2005 there is a slight distance. The scanning bars 20. El and 22. 23. 24. 2000. 200]. 2003. 2004. 2005. Zlllll l. 2021. BUZZ. and 2032 can be made of an insulating material. e.g.. wood. plastic material. and the like.

When a failure occurs which causes the shed to be not fully open. an increased pressure of the carrier 3 upon the scanning bar 20 is induced. As a consequence. the scanning bar 20 will be deviated upwards. thus closing the electrical circuit by the switch element 40]. An electrical impulse thus generated is fed into the control 45 of the machine drive P. and caused the stopping of the maching. The functions of the described constructions according to FIGS. 4- ]2 inc. are the same as those immediately described above.

The converters used are not confined to those described above The motion ofthe bar 20 can be further emplo ed in connection with a piezoelectric crystal and also with tensometric particles. and the respective electric circuits. respectively.

Mechanical stops S8. 5!. 582. 583 serve to protect the inner contact elements from damage in cases when the force upon the scanning bars 2". 2001, 2002. 2003. Ztlll-l. and 2005 is excessive.

It is possible to control reliably the carriers 3 by means of the described device from the viewpoint of eventual resistances against the movement of the carriers in the entry end zone A. in the entry transferring zone B where the carriers 3 arrive among the warp threads 4i into the shed. in the shed zone (I. in the exit transferring zone D in which the carriers 3 leave the shed. as well as in the exit end zone E.

Although the invention is illustrated and described with reference to a plurality of preferred embodiments thereof. it is to be expressly understood that it is in no way limited to the disclosure of such a plurality of preferred embodiments. but is capable of numerous modifications within the scope of the appended claims.

What is claimed is:

l. A method ofcontrolling weft carriers which move along a carrier guide in travelling shed weaving machines provided with a machine drive and a controller for said drive. comprising monitoring any increased resistance to travel of the carriers during their operative movement resulting in a deflection of the carrier guide. detecting and converting the deflection of the carrier guide into an electrical signal. and forwarding such signal to the controller of the machine drive to stop the machine when the deflection of the carrier guide es ceeds a predetermined desired value.

2. A method according to claim l. comprising monitoring the increased resistance to travel of the carriers separately in the following zones of their travel: the entry end zone. the entry transferring zone. the shed zone. the exit transferring zone and the exit end zone.

3. A method according to claim I. wherein the carriers move in a horizontal phase. and comprising monitoring the increases resistance to travel of the carriers during their operative movement as a function of the upward vertical deflection of the carrier guide.

4. A method according to claim 3. wherein the carriers move beneath a scanning bar which serves to guide the carriers. and detecting the vertically upward deflection of the scanning bar by the carriers as they move.

5. Apparatus for controlling weft carriers in travelling-shed weaving machines. provided with machine drive and a controller for said drive. comprising a guide for the carriers. said guide including a scanning bar along which the carriers travel. means for detecting and converting a deflection of the scanning bar into electrical signal. and means for forwarding such signal to the controller of the machine drive to stop the machine when the deflection of the scanning bar exceeds a predetermined desired value.

6. Apparatus. according to claim 5, wherein the car riers move in a horizontal phase. and comprising an upper guide for the carriers. such guide including a scanning bar beneath which the carriers travel. and means for detecting the vertical force exerted on the scanning bar by the carriers as they move.

7. Apparatus. according to claim 6. comprising a transducer connected to the scanning bar. upon vertically upward displacement of the scanning bar. said transducer generating said signal which is forwarded to the controller for stopping the machine.

8. Apparatus. according to claim 7. wherein the transducer is a bellows of variable volume connected to a constant manostat spring-loaded between the scanning bar and the rigid cross-beam.

9. Apparatus. according to claim 7. comprising elastic members disposed between the scanning bar and the rigid cross-beam. the rigid cross-beam having stops defining the range of movement of the scanning bar.

10. Apparatus. according to claim 9. wherein the rigid cross-beam carrying the scanning bar is affixed to the draw rod of a lifting mechanism.

ll. Apparatus. according to claim 6. wherein the scanning bar is divided into parts including the following: an entry end scanning bar. an entry transferring scanning bar. a shed scanning bar. an exit transferring bar. and an exit end scanning bar. and comprising a transducer for each of said scanning bars; said trans ducer being disposed for operation by their respective parts of the scanning bar; the transducers being connected to the controller for stopping the machine.

12. Apparatus according to claim 11, wherein the adjacent ends of the scanning bars are cut askcw of the warp threads.

13. Apparatus. according to claim 6, wherein the scanning bar is displaceablc from its operating position to a non-operating position. and vice versa.

14. Apparatus. according to claim ll, wherein the entry end scanning bar. the entry transferring bar. the shed scanning bar. the exit transferring bar. and the exit end scanning bar are displaceable from their operating position to a non-operating position. and vice versa.

15. Apparatus. according to claim 6. wherein the shed scanning bar is divided into independent scanning sections. each sections being displaceable into nonopcrating position.

16. Apparatus. according to claim 6. wherein the scanning bar is swingable in the range between stops seated on an arm. the scanning bar being pressed into basic position by a spring. the scanning bar in the scanning position being in contact with the transducer. such transducer being fixed on the arm.

17. Apparatus. according to claim 16. wherein the arm is affixed to a rotatable shaft for deflecting the scanning bar into non-operating position.

LII

contact points, confronting the scanning bar; the reinforced beam being insulated from the cross-beam. the assembly being mounted upon a vertically adjustable support.

21. Apparatus. according to claim 6. wherein the transducer is a condenser which changes its capacity when the scanning bar is deflected. the condenser having opposed electrodes mounted respectively on the scanning bar and adjustable. 

1. A method of controlling weft carriers which move along a carrier guide in travelling shed weaving machines provided with a machine drive and a controller for said drive, comprising monitoring any increased resistance to travel of the carriers during their operative movement resulting in a deflection of the carrier guide, detecting and converting the deflection of the carrier guide into an electrical signal, and forwarding such signal to the controller of the machine drive to stop the machine when the deflection of the carrier guide exceeds a predetermined desired value.
 2. A method according to claim 1, comprising monitoring the increased resistance to travel of the carriers separately in the following zones of their travel: the entry end zone, the entry transferring zone, the shed zone, the exit transferring zone and the exit end zone.
 3. A method according to claim 1, wherein the carriers move in a horizontal phase, and comprising monitoring the increases resistance to travel of the carriers during their operative movement as a function of the upward vertical deflection of the carrier guide.
 4. A method according to claim 3, wherein the carriers move beneath a scanning bar which serves to guide the carriers, and detecting the vertically upward deflection of the scanning bar by the carriers as they move.
 5. Apparatus for controlling weft carriers in travelling-shed weaving machines, provided with machine drive and a controller for said drive, comprising a guide for the carriers, said guide including a scanning bar along which the carriers travel, means for detecting and converting a deflection of the scanning bar into electrical signal, and means for forwarding such signal to the controller of the machine drive to stop the machine when the deflection of the scanning bar exceeds a predetermined desired value.
 6. Apparatus, according to claim 5, wherein the carriers move in a horizontal phase, and comprising an upper guide for the carriers, such guide including a scanning bar beneath which the carriers travel, and means for detecting the vertical force exerted on the scanning bar by the carriers as they move.
 7. Apparatus, according to claim 6, comprising a transducer connected to the scanning bar, upon vertically upward displacement of the scanning bar, said transducer generating said signal which is forwarded to the controller for stopping the machine.
 8. Apparatus, according to claim 7, wherein the transducer is a bellows of variable volume connected to a constant manostat spring-loaded between the scanning bar and the rigid cross-beam.
 9. Apparatus, according to claim 7, comprising elastic members disposed between the scanning bar and the rigid cross-beam, the rigid cross-beam having stops defining the range of movement of the scanning bar.
 10. Apparatus, according to claim 9, wherein the rigid cross-beam carrying the scanning bar is affixed to the draw rod of a lifting mechanism.
 11. Apparatus, according to claim 6, wherein the scanning bar is divided into parts including the following: an entry end scanning bar, an entry transferring scanning bar, a shed scanning bar, an exit transferring bar, and an exit end scanning bar, and comprising a transducer for each of said scanning bars; said transducer being disposed for operation by their respective parts of the scanning bar; the transducers being connected to the controller for stopping the machine.
 12. Apparatus according to claim 11, wherein the adjacent ends of the scanning bars are cut askew of the warp threads.
 13. Apparatus, according to claim 6, wherein the scanning bar is displaceable from its operating position to a non-operating position, and vice versa.
 14. Apparatus, according to claim 11, wherein the entry end scanning bar, the entry transferring bar, the shed scanning bar, the exit transferring bar, and the exit end scanning bar are displaceable from their operating position to a non-operating position, and vice versa.
 15. Apparatus, according to claim 6, wherein the shed scanning bar is divided into independent scanning sections, each sections being displaceable into non-operating position.
 16. Apparatus, according to claim 6, wherein the scanning bar is swingable in the range between stops seated on an arm, the scanning bar being pressed into basic position by a spring, the scanning bar in the scanning position being iN contact with the transducer, such transducer being fixed on the arm.
 17. Apparatus, according to claim 16, wherein the arm is affixed to a rotatable shaft for deflecting the scanning bar into non-operating position.
 18. Apparatus, according to claim 16, wherein the stops are adjustable.
 19. Apparatus, according to claim 6, comprising electrically insulating elastic members aligned between the scanning bar and a rigid cross-beam, and a ribbon-like contact electrode disposed normally spaced from the scanning bar.
 20. Apparatus, according to claim 6, comprising an assembly of a rigid cross-beam to which the scanning bar is secured, and a reinforced beam equipped with contact points, confronting the scanning bar; the reinforced beam being insulated from the cross-beam, the assembly being mounted upon a vertically adjustable support.
 21. Apparatus, according to claim 6, wherein the transducer is a condenser which changes its capacity when the scanning bar is deflected, the condenser having opposed electrodes mounted respectively on the scanning bar and adjustable. 